The postnatal subventricular zone (SVZ) is a germinal zone containing distinct immature cell types, including stem cells and migrating neuronal progenitors. Understanding the in situ physiological properties of SVZ cells and the diffusible factors influencing SVZ cell physiology is critical to allow endogenous activation of stem cells/progenitors and induction of self-repair. In situ SVZ cell physiology and SVZ signaling factors are, however, largely unknown. Because the identity of neural stem cells is still debated, we propose to identify the signaling factors that regulate SVZ cell properties and could in particular influence neuronal progenitor migration. GABA is a likely candidate as a signaling factor because it regulates migration of embryonic cells and its synthetic enzyme is present in the SVZ. We thus hypothesize that GABA is a signaling factor locally released by migrating progenitors at rest resulting in activation of GABA autoreceptors and ion channels known to be involved in cell migration. The two following aims will be addressed with whole-cell and perforated patch-clamp recordings, and with fluorimetric Ca2+ measurements in SVZ slices. The first aim will determine whether GABA activates GABA receptors (GABAR5) on neuronal progenitors and whether GABAR activation leads to Ca2+ increase and Ca2+-dependent K+ (KCa) channel activation, which triggers membrane potential changes. KCa channel activation is known to be a prerequisite for migration of other cell types. The second aim will investigate whether GABARs are activated by transport-mediated GABA efflux from progenitors following membrane potential depolarization. Neuronal progenitors will be recorded from transgenic mice expressing yellow fluorescent protein in such progenitors under the control of the tubulin promoter. Data from these studies will provide the first fundamental insight into the physiology of SVZ cells in situ and exposes a novel concept of cell migration governed by an interplay between GABARs and GABA transporters.